Dictionary of Electronics
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BCD to Decimal Converter

Binary Coded Decimal. [BCD] is a number system that only counts from 0 to 9 and then repeats. The table below shows the conversion between the different numbering systems and BCD code.
BCD is also called 8421 because the binary LSB counts as a 1, the next bit adds 2, than 4 and the final MSB bit adds 8 to the final numbers. So a BCD 1001 is equal to 8 plus 1 or decimal 9 [as the table shows].

The table below provides the conversion between Binary [Base 2], Decimal [Base 10], Hexa-decimal [Base 16], Octal [Base 8], BCD Code, and Gray Code.

BCD Table
Conversion Table

Circuit to convert Binary coded decimal to decimal. Using standard glue logic ICs; note the circuit works regardless of the particular logic standard used, as long as those families can communicate with each other over the same voltage levels. Manufacturers of Standard Glue Logic

BCD Circuit

Binary Coded Decimal Converter circuit
BCD Converter Schematic

This IC circuit is used to convert 4-bit BCD code to Decimal using the circuit shown.
The schematic shows a 4-bit converter circuit, because BCD only uses 4-bits. There are nine bits on the output because decimal counts from zero to nine

7445 True Table
7445 BCD Decimal Decoder True Table

The true table for the BCD to Decimal Decoder is shown above. The output is active low and counts from 0 to 9 decimal. When all BCD inputs are low '0', output 0 is low and so on. Note that this circuit only counts to 9, so any input higher than '9' results in all the outputs going high. So even as the inputs continue to change the output remains unchanged in the last six entries.

BCD to Binary Coded Decimal ICs
7445, 5445 ... 7447, 5447 ... 74145, 54145
Functionality there is no difference between a 74xx part and a 54xx part. The difference between a 74x and 54x part is their Operating Temperature Ranges. Also refer to a Decimal to BCD Encoder [Binary coded decimal decoder].

The IC schematic below represents the same circuit as above, but using negative logic.

Binary Coded Decimal Converter, Negative Logic
BCD Decoder Schematic, Negative Logic

This page shows a Gray Code to Binary coded decimal decoder. The circuit can be made with XOR gates.

There are a number of different ways to represent a logic function. The circuit above shows a different representation than the circuit at the top of the page. Regardless of the logic function the circuit translates a 4-bit BCD code into a 9-bit Binary code.

What is a BCD. How to convert BCD Code. Define BCD Code.

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